There are several rumours circulating about 'deals' done in Zimbabwe. Most are wishful thinking as they do not address the underlying facts.
1. Emmerson Mnangagwa was legally and constitutionally fired as Vice-President. He is not 'in line' for the succession as a matter of right.
2. The military cannot call what they did a 'coup' as this would automatically involve the AU and SADC in the solution to the crisis.
3. There is no constitutional reason for Mugabe not to serve out his term unless he voluntarily steps down or is impeached.
4. The military cannot suspend the constitution without making it a "de facto" coup.
5. The Constitution provides that if the President steps down there must be an election within 90 days. There is no constitutional or legal provision for a 'transitional' government. If Emmerson or Sidney run for the leadership of ZANU-PF they can submit their name as a candidate in the election. The other parties can submit their own candidates.
6. Until there is a change in Mugabe's position (either by retirement or impeachment) the existing government continues unchanged. There may be new Cabinet members and there may be trials but the military cannot change the constitution without that becoming a 'coup'. Non ZANU-PF people can be brought into the government to promote peace and co-operation (this was done before) but Mugabe remains the head of state.
So, extra-constitutional schemes will ultimately come up against the constraints listed above.